This invention generally relates to vehicle transmissions. More particularly, this invention relates to a manual vehicle transmission with an automated device that functions as a combined clutch range shift gear box.
Manual vehicle transmissions are well known. Typical arrangements include a main gear box having a plurality of gear members that are selectively, manually engaged to achieve a desired gear ratio. Typical systems also include a clutch for selectively coupling a transmission input shaft to an engine output shaft. The clutch must be operated to allow a driver to shift between the various gear ratios that are available. Some systems include a range gear box that allows the main gear box members to be utilized for two sets of gear ratios; a low range and a high range.
The task of driving a vehicle having a manual transmission can prove difficult for many drivers and, in many circumstances requires highly skilled operation. In heavy vehicles, such as trucks, with a large number of available gear ratios, the driver must be able to coordinate manual shifting, manual clutch operation and manual throttle control of the engine to achieve the conditions necessary to effect efficient shifting. Various attempts have been made to simplify the task of driving vehicles with manual transmissions.
One approach has been to automate the clutch operation. An example of this approach is shown in U.S. Pat. No. 4,981,202, where an electric motor is used to open and close a clutch as needed during shifting. Another approach at simplifying the shifting operation of a manual transmission, has been to control the torque between the engine and the transmission without actuating the clutch. An example of this approach is shown is U.S. Pat. No. 5,569,115, where synchronization techniques are used to control the torque between the engine and the transmission to allow a driver to shift gears without requiring clutch operation. Another approach at simplifying the operation of a manual transmission is to provide the driver with a shift lever that generates electrical signals indicating a desired gear shift. An automated shift actuator moves the components within the transmission gear box in response to the signal generated by the driver moving the shift lever.
While the above systems each have their own advantages and benefits, those skilled in the art always strive to make improvements. Additionally, some of the proposed or current systems have certain drawbacks and shortcomings. For example, electric clutch actuators require additional components, which introduces additional cost. Further, the of electrical clutch actuators can introduce the need for further maintenance and repair.
Another aspect of simplifying the operation of a manual transmission relates to the use of a range gear box. In some circumstances, a manual operation of a range shift is required. Other proposals have included automating a range gear box under conditions where a shift between high and low ranges is required (i.e. between fifth gear and sixth gear). One example of a proposed arrangement for a hydraulically operated range gear system is shown in U.S. Pat. No. 4,403,526 where a planetary gear set is provided that operates as a range gear box.
This invention provides a significant advance compared to previous systems by integrating the function of a traditional clutch and a range gear box into a single device that operates in conjunction with the main gear box. A transmission system designed according to this invention does not include the traditional clutch and, therefore, does not require a driver to operate a clutch pedal. Further, this invention does not require any additional automated clutch operating mechanism. This invention provides manufacturing economies and enhanced vehicle performance compared to traditional arrangements.
In general terms, this invention is an integrated manual transmission system having a single device that combines the function of a traditional clutch and a range gear box. A transmission system designed according to the invention includes a main transmission gear box with a plurality of gear members that are selectively engaged to provide a plurality of gear ratios between a transmission input shaft and a transmission output shaft. The transmission input shaft preferably is directly coupled to a rotary output member on the vehicle engine such as the engine output shaft or the flywheel. A shift member allows a driver of a vehicle to manually select one of the plurality of gear ratios. A planetary gear arrangement is selectively operated to couple the transmission input shaft to the transmission output shaft such that the force from the engine output member is selectively transferred through the planetary gear arrangement and the main gear members to the transmission output shaft.
In the preferred embodiment, the planetary gear arrangement includes a sun gear, a ring gear and a plurality of pinion gears that are associated with a carrier member. The carrier member preferably is associated with the gear members in the main gear box so that torque imposed on the carrier member is transferred through the main gear box to the output shaft. Either the sun gear or the ring gear can be coupled to the transmission input shaft to rotate with the rotating engine output member. An automated engaging member, such as a wet clutch, is operated to selectively provide a first reduction ratio between the transmission input shaft and the main gear box, a second gear reduction ratio, and to effectively uncouple the transmission input shaft from the transmission output shaft to allow a shift in the main gear box.
The planetary gear arrangement replaces a conventional clutch and separate range gear box assembly. A system designed according to this invention automates a portion of the operation of a manual transmission system, which simplifies the task of driving the vehicle. Moreover, a system designed according to this invention provides enhanced drive line and vehicle performance and manufacturing advantages.
The various features and advantages of this invention will become apparent to those skilled in the art from the Detailed Description of the currently preferred embodiment. The drawing that accompany the Detailed Description can be briefly described as follows.